This invention relates to an analog/digital compatible reproducing system applied particularly to a digital audio tape recorder of a stationary head system (S-DAT) for reproduction or recording/reproduction, so as to be capable of reproducing a normally analog recorded tape, for example, the compact cassette tape, and a tape cassette usable in such a system.
Recently, the digital recording audio tape recorder DAT has achieved remarkable development and popularization. However, since the usual cassette tape, or compact cassette audio tape is in extremely widespread use, the general users have a large number of recorded compact cassette tapes and thus use a conventional analog tape recorder and DAT. This causes great inconvenience, particularly for the user of the portable tape recorder of a pocket-size or the like.
An S-DAT (stationary head digital audio tape recorder) has substantially the same construction or hardware as does the conventional analog cassette system (player and recorder) except it has a multitrack head and is able to reproduce the analog signal recorded on the conventional compact cassette or record an analog signal on the compact cassette, and can further record and reproduce a digital signal, or is constructed to have the compatibility for both digital and analog recording/reproduction.
In this case, the cassette tape exclusively used for the S-DAT is produced according to the same specification as the conventional compact cassette B shown in FIG. 20 which is exclusively used for analog recording as will be understood from the above description. Therefore, particularly a reel hub 122 shown in FIG. 21, around which a magnetic tape 121 is wound has 6 ratchets 124 provided at an equal pitch on the inner wall of a cylindrical body 123 so as to project towards its center in the same way as in the conventional compact cassette B. A reel table 125 provided in the tape cassette holding portion of the S-DAT is matched with the shape of the reel hub 122. As shown in FIG. 22, this reel table has a reel shaft 126 at its center and this reel shaft 126 has 3 engaging projections 127 integrally provided around the reel shaft 126 at an equal pitch, as in the conventional analog cassette system. The three engaging projections 127 are inserted in recesses 128 which are formed between the ratchets 124 of the reel hub 122, when a tape cassette exclusively used for the S-DAT is loaded in the tape cassette holding portion of the S-DAT, or when the reel hub 122 is fitted on the reel table 125. When the reel table 125 is rotated in one direction as a rotating shaft 129 rotates, the reel hub 122 is rotated while the engaging projections 127 of the reel table 125 engage with the ratchets 124 of the reel hub 122. Thus, when this reel hub 122 ratchets, the magnetic tape 121 is wound on the other reel hub 122, and is transported past the head so that, for example, analog and digital reproduction is automatically made. Since the specification of the S-DAT tape cassette is the same as that of the conventional compact cassette B, the tape cassette for S-DAT has a mark (for example, detection hole or the like) provided for mechanically or electrically distinguishing from the conventional compact cassette.
The tape cassette exclusively used for S-DAT which has been discussed can be loaded in the normal analog cassette system since it has the same specification as the conventional compact cassette B. When the S-DAT tape cassette is recorded with a digital signal, however, the digital signal cannot be reproduced by the normal analog cassette system. This, the general user will inevitably load the S-DAT tape cassette in the normal analog cassette system without knowing it. Thus, in order to distinguish the S-DAT tape cassette from the conventional tape cassette, the general user will have to put an identification mark on the label, and finally will have no choice but to try to load the tape cassette in the analog cassette system and to reproduce it, thus probably getting confused in using tape cassettes. Moreover, since the idea of the compatibility for the digital and analog recording/reproduction is not yet fully understood by the general user, the S-DAT tape cassette may be mistaken for the compact cassette. In that case, since the S-DAT can not be reproduced, it may be regarded as being defective.